In the cutting machining of slots of gearwheels, with working teeth, or spline joints, with non-working teeth, it is, using today's technique, generally difficult to provide a final shape of the so-called root of the tooth slots 82 between adjacent teeth 83, i.e., the bottom surface 81 of the tooth slots 82 and the area at the bottom of the tooth slots 82, see FIG. 18, particularly of the shaft 80 of the spline joint. This difficulty may also be present in the hub 90 of the spline joint. Today, the machining of such slots is carried out in several steps where the shape of the root, or final shape is achieved by subsequent machining steps, including milling using another milling insert and grinding in another machine and in another set-up, which thereby imposes requirements of a preceding measurement of the workpiece before the final machining.
Spline joints formed according to ISO14 may have a so-called bottom guide, which means that centering of the spline joint is effected by means of bottom surfaces 81 of the tooth slots 82 in the shaft 80. These bottom surfaces 81 also form the abutment surfaces of the shaft 80 against the hub 90. In these spline joints, there is simultaneously a gap between the outer peripheral surface 91 of the teeth 83 of the shaft 80 and the tooth slots 92 of the hub 90.
It will be appreciated that the important abutment surfaces of the shaft 80 and the hub 90 have to have high tolerances, which most often are obtained by the surfaces being ground. In order for the bottom surfaces 81 of the shaft 80, which form abutment surfaces, to be possible to be ground, it is required that the shaft 80 has undercuts 84 between the bottom surfaces 81 of the tooth slots 82 and the flank surfaces 85 of the respective adjacent tooth 83.
Normally, a shaft is manufactured by milling out the gaps one by one, to a radius that is greater than the final radius of the guide surfaces. This may be done by a slitting cutter, which rotates on its own center shaft and the workpiece, wherein the shaft is fed forward in its longitudinal direction. This operation may also be made by a hob tool. In such a tool, the cutting inserts are placed along a helical line of several turns, along a cylindrical tool body. At the same time as the tool rotates, the workpiece (the shaft) also rotates and either the shaft or the tool is simultaneously linearly fed in the longitudinal direction of the shaft.
In the next step, the above-mentioned undercuts 84 are created by, for instance, slit cutting, hobbing, or in some other suitable way.
In the third step, the surfaces are machined to the desired circular and cylindrical shape, wherein the guide surfaces, in this case the bottom or abutment surfaces of the shaft between the teeth, obtain the final radius.
EP-B-580591 discloses a milling tool formed for cutting rough machining by the milling of slots of gearwheels. The milling tool includes a plurality of segments, each one of which has a plurality of cutting blades arranged one after the other. The segments are different and formed for rough machining, semi-fine machining and final machining. EP-B-580591 discloses cutting blades for rough machining. Each such cutting blade comprises an under side, an opposite upper side forming a chip surface, and an edge side between the upper side and the underside. A shaft extends through the underside and the upper side. A cutting edge extends between the edge side and the chip surface and is partly formed to be in engagement with the workpiece. The cutting edge comprises a relatively short primary side cutting edge, a relatively short secondary side cutting edge, as well as a relatively long front cutting edge, which borders on and connects the primary side cutting edge and the secondary side cutting edge. The front cutting edge may have a different design with a curvature. These designs of the front cutting edge have the function of influencing the chip removal and the strength of the cutting blade.
US 2008/0206007 discloses another milling tool for cutting rough machining by the milling of slots in a turbine disk. Each slot is, after a subsequent final machining, formed to receive and hold a turbine blade in the turbine disk. The milling tool comprises a plurality of cutting inserts having a cutting edge, which comprises a primary side cutting edge, a secondary side cutting edge, and a front cutting edge, which connects the primary side cutting edge and the secondary side cutting edge.
DE-929 588 discloses a milling tool for the milling of teeth. The milling tool comprises a plurality of cutting inserts, each one of which has a front cutting edge and a co-lateral cutting edge. The front cutting edge borders directly on the co-lateral cutting edge.
EP 1356885 discloses another type of cutting insert formed to be mounted in a milling tool for the milling of camshafts. The cutting insert comprises an under side, an opposite upper side, and an edge side, which forms a chip surface. The principal clamping direction for the attachment of the cutting insert extends radially in the milling tool.
US 2003/0165363 discloses an additional example of a type of cutting insert formed to be mounted in a milling tool for the milling of camshafts.
US 2003/0005803 discloses another example of a cutting insert formed to be mounted in a milling tool for the milling of camshafts.